Mimicry

Animal Sciences
COPYRIGHT 2002 The Gale Group Inc.

Mimicry

Animals that are toxic, armed with spines, or are otherwise unpalatable, or disagreeable, to predators often exhibit conspicuous colors or patterns. These superficial characteristics, called aposematic signals, are used to warn potential predators of the animal's physical or chemical defenses. The distinct colorations are highly conspicuous against certain backgrounds. This imposes a cost on the aposematic prey because the predators can more readily spot them. However, the predators will also be quick to learn and remember which prey to avoid because of the distinctiveness of the signals. Of course, if the prey is not sufficiently unpalatable, then the costs are greater than the benefits for the attacked animal.

To evaluate whether the benefits outweigh the costs of any predator/prey strategy, the Evolutionary Stable Strategy (ESS) should be taken into
account. The ESS is a strategy that, when common among members of a particular role—such as aposematic coloration of prey—is not invaded or displaced over evolutionary time by any rare alternative. In addition, at evolutionary stability, each role has its own ESS.

An important aspect of aposematic signaling is the evolution of another defense, mimicry. A mimic is a predator or prey that bears a superficial resemblance to another species. The mimic resembles the model, which exhibits aposematic coloration. There are two forms of mimicry: Batesian mimicry and Mullerian mimicry.

In Batesian mimicry, a palatable species mimics an unpalatable model, thereby gaining protection through the traits of another species. For example, juveniles of the harmless lizard species Heliobolus lugubris, inhabitants of the Kalahari Desert of southern Africa, mimic the color and posture of the ooglister beetle, a species that sprays noxious fluids at predators. As the lizards mature and grow larger than the average beetle, they develop cryptic coloration as a line of defense.

Another example is the monarch butterfly. Monarch butterflies store cardiac poisons acquired from milkweed plants they eat as larvae and are therefore distasteful and potentially harmful to other species. Viceroy butterflies, by contrast, are harmless and palatable and so need a good defense to ward off predators. The viceroy is protected by having wings of the same coloration pattern as the monarch butterfly. Many innocuous snakes mimic the conspicuous red, white, and black markings of the poisonous coral snake in an attempt to protect themselves.

It is important to note that for Batesian mimicry to be effective, there must be a larger population of models than mimics so that predators are not clued in to the fact that they are being tricked.

Mullerian mimicry involves two or more unpalatable, aposematically colored species that resemble each other in appearance. This strategy evolved so that predators will learn more quickly to avoid animals with particular warning signs.

Some predators practice a reverse mimicry in order to trap their prey. Some species of snapping turtles, for example, have tongues that resemble wriggling worms. By sticking their tongues in the water, these turtles are able to lure small fish that are looking for a meal of worms.

Although mimicry seems a rather straightforward tactic, several conditions must be met in order for it to function as an ESS. The first condition for the strategy to be successful is that very conspicuous signals of aposematic coloration should be avoided so that it is somewhat difficult for predators to learn to avoid the aposematically patterned prey. Second, increasing prey unpalatability should increase the chances that any attacked prey will survive because the predator will quickly learn species avoidance after attacking the prey. It is important to note that the degrees of unpalatability and signal conspicuousness at ESS depend on the predators' patterns of learning .

Despite all the warning patterns and colors, predators do sample aposematic prey on occasion. And although Mullerian mimicry is found among quite a few species, Batesian mimicry is considered a rare defensive strategy. The balance between the employment of mimicry and its success rate supports the notion that these aposematic signals are a relevant ESS.

mimicry

The Columbia Encyclopedia, 6th ed.

Copyright The Columbia University Press

mimicry, in biology, the advantageous resemblance of one species to another, often unrelated, species or to a feature of its own environment. (When the latter results from pigmentation it is classed as protective coloration.) Mimicry serves either to protect the mimic from its predators, as when the model is inedible or dangerous, or to deceive its prey (e.g., certain ant-eating spiders that themselves resemble ants). Mimicry occurs in both plants and animals but is most prevalent among insects, particularly butterflies and moths. The first scientific studies on the subject were published by English naturalists H. W. Bates (1862) and A. R. Wallace (1865). The Batesian theory is based on the operation of natural selection: if, say, a harmless snake acquires a deceptive resemblance to a poisonous variety it is then more likely to escape its predators and thus to survive and propagate, producing offspring with the same appearance. Examples of mimicry are the resemblance of the viceroy butterfly to the monarch butterfly, which is repugnant to birds; harmless nettles that resemble stinging nettles; and the many fishes, crabs, and slugs of the Sargasso Sea that resemble the floating seaweed masses they inhabit.

mimicry

mimicry The resemblance of one animal to another, which has evolved as a means of protection. In Batesian mimicry, named after British naturalist Henry Bates (1825–92), the markings of certain harmless insects closely resemble the warning coloration of another insect (the model). Predators that have learnt to avoid the model will also avoid good mimics of it. This phenomenon is often found among butterflies. Müllerian mimicry, named after German zoologist J. F. T. Müller (1821–97), involves the mutual resemblance of a group of animals, all harmful, such as the wasp, bee, and hornet, so that a predator, having experienced one, will subsequently avoid them all.

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mimicry

mimicry Form of animal deception, either for protection or to lure prey. The mimic, generally a harmless edible species, protects itself by imitating the warning shape or coloration of a ‘model’, a poisonous or dangerous species. When coloration increases an animal's chances of survival, as seen in the chameleon, it is commonly referred to as protective coloration. Examples of mimicry to capture prey include the anglerfish that waves a fleshy wormlike extension from his snout, and spiders that resemble ants, their prey.

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mimicry

mim·ic·ry
/ ˈmiməkrē/
•
n.
(pl. -ries)
the action or art of imitating someone or something, typically in order to entertain or ridicule:
the word was spoken with gently teasing mimicry |
a playful mimicry of the techniques of realist writers. ∎ Biol.
the close external resemblance of an animal or plant (or part of one) to another animal, plant, or inanimate object. See also Batesian mimicry, Müllerian mimicry.

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